1. Field of the Invention
The present invention relates to a wireless sensor device having a so-called sensing function, which is capable of reading out information without contact, e.g., by radio communication. In particular, the invention relates to a wireless sensor device which is used while being implanted in, swallowed by, or attached to the living body.
2. Description of the Related Art
Nowadays, an increasing number of information is being processed with the development of IT technology. Among them is the information management for human health. For example, health checkups are regularly conducted at companies, schools, and the like; individuals are informed of their heath conditions at least once or twice a year. When the condition of one's health is not good, he/she will be noticed of the fact and receives treatment at a hospital.
Also, simple health measurement instruments for domestic use have been developed for easy checkups of one's health conditions. In recent years, portable measurement instruments have also become widespread, contributing to early detection of diseases.
Reference 1 (Japanese Published Patent Application No. 2004-121632) is one of the examples of the heath measurement instrument.
Reference 1 discloses a portable blood-pressure measurement instrument. Using such a measurement instrument, one can easily know his/her health condition.
However, the conventional health measurement instrument disclosed in Reference 1 has the following problems: even though the size of the health measurement instrument is reduced to some extent, it is still large for being carried around. Moreover, even when a user acquires information with the measurement instrument, he/she may be unconscious of a change in physical condition because the information cannot be immediately seen by a medical specialist. This could result in a progression of disease.
In view of the foregoing, a semiconductor device having a function of wirelessly acquiring physical information has been devised, for example by attaching a sensor device having a radio function to a human body. A specific example thereof is disclosed in Reference 2 (Japanese Published Patent Application No. 2006-99757). In this example, physical information in particular can be acquired with a dedicated wireless reader device without the help of medical institutions and the like.